1. Field of the Invention
One or more embodiments of the present invention relate to a machine tool such as a machining center and, more particularly, to a horizontal machine tool with a spindle in a horizontal orientation.
2. Background Art
As a horizontal machine tool, there are known related-art machining centers as described in Patent Literatures 1 to 4.
In Patent Literature 1, a gantry column which is a structure separate from a base stands on the base by being fixed by bolts. X-axis guide rails are provided to upper and lower portions of a front side of the gantry column and a saddle is guided by the X-axis guide rails to be movable in a left-right direction. The saddle is provided with Y-axis guide rails and a spindle head is guided by the Y-axis guide rails to be movable in a vertical direction. In this way, the spindle is movable in the left-right and vertical directions.
Patent Literature 2 discloses a machining center in which a spindle is movable in a front-back direction (Z-axis direction) in addition to the same structure as that in Patent Literature 1.
A machining center in Patent Literature 3 includes: a bed having a base portion and a pair of side walls standing on opposite end portions of the base portion; a frame-shaped first feed table supported on back faces of the respective side walls of the bed and movable in a vertical direction; a second feed table disposed in the frame of the first feed table and movable in a left-right direction; a spindle head disposed in a through hole provided in the second feed table and movable in a front-back direction; and a spindle supported on the spindle head.
A machining center in Patent Literature 4 includes: a base frame on which a workpiece support face is formed; an X-axis saddle mounted to a back face portion of the base frame to be movable in a left-right direction with an X-axis movement mechanism interposed therebetween; a Y-axis saddle mounted to a back face portion of the X-axis saddle to be movable in a vertical direction with an Y-axis movement mechanism interposed therebetween; and a spindle unit mounted to an upper face portion of an extending portion of the Y-axis saddle to be movable in a front-back direction with a Z-axis movement mechanism interposed therebetween.